Japan was one of the earliest countries to participate in Atoms for Peace, and has utilized research reactors and critical assemblies powered by HEU since the 1960s. However, the country became an early participant in civil HEU minimization efforts. 1978 marked the first meeting of the special "Five Agency Committee on HEU," which directed Japan's cooperation with the U.S. Reduced Enrichment for Research and Test Reactors (RERTR) program.

HEU Production, Use, and Commerce

Since 1992, Japan Nuclear Fuel Ltd. has produced low-enriched uranium (LEU) at Rokkasho for Japan's extensive nuclear power program. However, Japan does not produce HEU.

Currently, one Japanese research reactor (UTR KINKI owned by Kinki University) and two critical assemblies (KUCA, wet and dry cores, owned by Kyoto University Research Reactor Institute (KURRI), are still HEU-powered. [4] One other research reactor (NSRR) used HEU in the past and then transitioned to 19.89% LEU fuel, but is temporarily shut down. [5]

HEU used at Japanese research facilities was supplied by the United States and the United Kingdom. [6] Approximately 500 kg of HEU at Japan's FCA critical assembly, which started up in 1967, are of UK origin. [7] Between 1957 and 1994, the United States supplied 1,000 kg of U-235 to Japan contained in 2,054 kg of uranium. [8]

Japan has partnered with the United States to begin to return U.S.-origin spent fuel, approximately 656 kg kg of HEU since 1997. [9] In 2014, the Foreign Research Reactor Spent Nuclear Fuel (FRR SNF) Acceptance Program was extended. Although the FRR SNF program is set to end in 2019, an exception has been made with Japan, and work is expected to conclude by 2029. [10] All of the shipments from the JRR-3, JRR 4 and JMTR have been completed. Seven shipments of HEU spent fuel from KUR of Kyoto University had been completed by 2007. [11]

Efforts to Reduce and Eliminate Civilian Use HEU

Japan's two largest owners of HEU-fueled facilities, Kyoto University and JAERI, began to work with the RERTR program in 1978 and 1979, respectively. [12] The Five Agency Committee directed the RERTR program in Japan. The committee was active until 2000, but has not met since 2001 because the LEU conversion activities of the reactors under the RERTR program in Japan are in their closing phase. [13]

At the 2014 Nuclear Security Summit, Japanese and U.S. leaders agreed to remove and dispose of all highly enriched uranium and weapons-grade plutonium from the Fast Critical Assembly (FCA) at the Japan Atomic Energy Agency (JAEA) in Tokai Mura, Ibaraki Prefecture in Japan. [14] At the final NSS in 2016 it was announced that with U.S. assistance, the removal of all HEU and Plutonium from the FCA has been completed. [15] The amount of material to be eliminated was not specified in the Joint Statement. However, since the Japan Atomic Energy Commission (JAEC) annually issues the Current Situation of Plutonium Management for the purpose of enhancing transparency, the amount of plutonium is calculable, and is approximately 700 pounds, or 320 kilograms. [16] The amount of HEU is estimated to be about 214.5 kilograms, or 450 pounds of weapons-grade HEU. [17] Using the IAEA Significant Quantities definition, this is enough material for approximately 48 nuclear weapons. The United States will down-blend the HEU to low enriched uranium (LEU), and the plutonium will be prepared for final disposition. [18] The FCA is designed to test the criticality of fast-neutron-reactor cores, purposes for which it was considered to be technically difficult to use LEU instead of HEU. [19] The decision to eliminate all of the plutonium and HEU at the FCA is therefore a significant milestone in minimization efforts.

Japan is in the final stages of conversion and shutdown of most HEU-powered facilities. Since 1990, Japan has converted four operational research reactors, the JRR-3M, JRR-4, JMTR, and KUR (converted in 1990, 1998, 1994, and 2010, respectively). [20] The Japan Material Testing Reactor Critical Assembly (JMTRC) and the JRR-2 reactor were shut down in 1995 and 1996. Also shut down were the Toshiba Training Reactor (TTR) (2001), the Rikkyo TRIGA (2002), and the Musashi MuITR (2004). [21] Decommissioning of the Very High Temperature Reactor Critical (VHTRC) Assembly was completed in 2009, and the DCA (Deuterium Critical Assembly) decommissioning process is underway. Both facilities are located at JAEA's Oarai Research and Development Center. [22]

All new research reactors in Japan have been designed to use LEU fuel. In February 1991, the Japanese government cancelled the HEU-powered Kyoto University High Flux Reactor (KUHFR) Project. However, the U.S.-origin HEU fuel intended for use in this reactor was used in the Kyoto University Research Reactor (KUR) until February 2006, following U.S. approval in April 1994. The United States has been repatriating the fuel at Kyoto University; the full core conversion from HEU to LEU of the KUR was successfully completed in March 2010. [23]

Two HEU-powered facilities, the Kyoto University Critical Assembly (KUCA), operated by Kyoto University's Research Reactor Institute, and the UTR KINKI research reactor, operated by Kinki University, are currently undergoing conversion feasibility studies. The aim is to initiate conversion of these reactors to LEU within the next four years. [24] Since 2008, Kyoto University and the U.S. Department of Energy's Argonne National Laboratory have been conducting joint feasibility studies for KUCA with the aim of substituting LEU-based fuel for the existing HEU. [25] In March 2012, the United States and Japan also agreed to launch joint feasibility studies on how to operate the UTR KINKI research reactor using LEU instead of HEU. [26] The YAYOI reactor operated by Tokyo University had employed HEU, but was permanently shut down at the end of March 2011 after 40 years' operation. It was decided that the spent HEU fuel from the reactor would be transferred to the JAEA. [27]

As part of Japan's efforts to minimize civilian use of HEU, the JAEA has developed technology to generate the medical isotope Molybdenum 99 without HEU. This new technology is expected to produce between one-fifth and one-fourth of the quantity required for Japan's domestic market. As a next step, the JAEA has to conduct technology demonstration tests at its JMTRC. [28]

As an active participant in HEU minimization efforts since their inception, Japan has made important contributions to minimizing the use of this material. However, Japan's policy on how to handle its HEU materials has been less clear, and there are simultaneous and interlinked concerns regarding Japan's policy on plutonium. [29] There have been some shipments of HEU spent fuel to the United States, but other HEU spent fuel remains in Japan. Japan has considered storing spent HEU fuel domestically, repatriating it to the United States, or sending it abroad to France or the United Kingdom for reprocessing. [30] Furthermore, while the JAEA and Kyoto University reportedly paid for spent fuel shipping, storage, and handling expenses related to repatriation operations, the Japanese government does not appear to have contributed money or manpower for this purpose. [31] Some Japanese institute officials have suggested that the Japanese government consider deeper engagement in repatriation operations. [32]

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About

The article is part of a collection examining civilian HEU reduction and elimination efforts. It details current Japanese HEU policies, progress reducing and eliminating the civil use of HEU in Japan, and remaining challenges.

About the Threats

This material is produced independently for NTI by the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2016.